It is not surprising that the impact of trauma often transcends generations; after all, the psychological and behavioral consequences can easily rub off on one’s children. But a recent finding from New York City’s Mount Sinai Hospital strongly suggests that trauma is not just socially conditioned, but genetically inheritable.
As the Guardian reports, the study analyzed the genes of children born to Jewish men and women who, in some way or another, had suffered during the Second World War (as camp internees, torture victims, being on the run, etc.). The offspring of these survivors were already known to have an increase chance of stress disorders, and sure enough, results showed that the region of a gene linked to stress was altered in a way not seen in the control group. (The research team confirmed that the changes were not due to any trauma experienced by the children themselves.)
[The] team’s work is the clearest example in humans of the transmission of trauma to a child via what is called “epigenetic inheritance” – the idea that environmental influences such as smoking, diet and stress can affect the genes of your children and possibly even grandchildren.
The idea is controversial, as scientific convention states that genes contained in DNA are the only way to transmit biological information between generations. However, our genes are modified by the environment all the time, through chemical tags that attach themselves to our DNA, switching genes on and off. Recent studies suggest that some of these tags might somehow be passed through generations, meaning our environment could have and impact on our children’s health.
Other studies have proposed a more tentative connection between one generation’s experience and the next. For example, girls born to Dutch women who were pregnant during a severe famine at the end of the second world war had an above-average risk of developing schizophrenia. Likewise, another study has showed that men who smoked before puberty fathered heavier sons than those who smoked after.
This marks the first time that the effects of stress have been demonstrated to pass on to children. It remains unclear how exactly these chemical tags get passed on, and whether or not the effect will permanently effect the children. What is certain, by empirical observation alone, is that those born and raised in communities with a long history of being oppressed, discriminated against, or tormented, tend to display psychological and behavioral pathologies typical of those actually suffering these transgressions.
Another study cited in the Guardian article, this time involving mice, found that even particular fears are inheritable.
Scientists at Emory University in Atlanta trained male mice to fear the smell of cherry blossom by pairing the smell with a small electric shock. Eventually the mice shuddered at the smell even when it was delivered on its own.
Despite never having encountered the smell of cherry blossom, the offspring of these mice had the same fearful response to the smell — shuddering when they came in contact with it. So too did some of their own offspring.
On the other hand, offspring of mice that had been conditioned to fear another smell, or mice who’d had no such conditioning had no fear of cherry blossom.
The fearful mice produced sperm which had fewer epigenetic tags on the gene responsible for producing receptors that sense cherry blossom. The pups themselves had an increased number of cherry blossom smell receptors in their brain, although how this led to them associating the smell with fear is still a mystery.
These findings have great implications for how to treat stress disorders, as well as how to address the collective psychological troubles that bedevil certain historically mistreated communities. They also confirm that progress takes time; even as one generation is lifted out of poverty, disease, hunger, and political repression, the psychological effects from these experiences linger on for at least another generation.
What are your thoughts?